Natural durability of four Tunisian Eucalyptus spp. and their respective compositions in extractives

Eucalyptus trees have been adapted to the Tunisian climate. Now, they need to be economically valued. Tunisian Eucalyptus have great technological properties allowing us to use them as wooden material. However, there is large variability in the natural durability between heartwood Eucalyptus spp. The wood sustainability assessment provides reliable parameters to predict the service life of wood-based products. This study aimed to evaluate the wood deterioration of four North Tunisian fast-growing Eucalyptus spp. (Eucalyptus maidenii, Eucalyptus saligna, Eucalyptus camaldulensis and Eucalyptus gomphocephala) exposed to basidiomycetes (Coniophora puteana and Trametes versicolor) and termite (Reticulitermes flavipes) attacks. Among the four Eucalyptus woods, Eucalyptus gomphocephala presents the highest decay and termite resistance. The four Eucalyptus wood species are classified as very durable against fungal degradation and durable against termite attacks, expect for Eucalyptus saligna which is classified as sensible against termites. The natural durability of Eucalyptus seems to be mainly caused by extractives, and a lot of compounds are involved. Antifungal and anti-termite properties of these compounds were put in perspective with the natural durability of wood. Gas chromatography-mass spectrometry (GC-MS) analyses highlighted that Eucalyptus durability is mostly governed by gallic acid, fatty acid glycerides, fatty acid esters, phenolic compounds, sitosterol, catechin and ellagic acid.